The present invention relates to a double yarn package composed of an elastic yarn, such as Spandex (polyurethane fiber), and a non-elastic yarn, such as wooly Nylon (stretch yarn made of polyamide) and obtained in such a condition that it can be effectively used in knitting operation on the knitting machine and it also relates to a method and apparatus for producing the same.
In obtaining a doubled yarn as described above, the use of a method in which a stretched elastic yarn and a non-elastic yarn are simply doubled together and wound into a cheese would result in only the elastic yarn cutting deep into the cheese due to its contractive force, causing the separation of the elastic and non-elastic yarns from each other when drawing out the doubled yarn as in knitting operation on the knitting machine, so that the elastic and non-elastic yarns cannot be drawn out in the same proportions and hence they cannot be used as a doubled yarn. Conventionally, in view of this fact, in order to obtain such doubled yarn a method has been employed in which a stretched elastic yarn is doubled with a non-elastic yarn and the doubled yarn is then twisted and heat-set, thereby twining both yarns together and setting them in that condition. Since such method involves heat-setting or other processes for setting the twisted condition, the manufacturing process is complicated and high speed production is impossible. Thus, the method has the disadvantage of being inefficient and uneconomical.
I have previously proposed a method of producing a doubled-yarn package of elastic and non-elastic yarns with the object of obtaining a yarn package enabling a doubled yarn composed of elastic and non-elastic yarns to be drawn out in the same proportions, wherein elastic and non-elastic yarns are doubled together and then twisted periodically and alternately in opposite directions, whereupon the doubled yarn is wound as a package such as a cheese or cone. According to this method, an elastic yarn which is in stretched condition is doubled and the resulting doubled yarn is wound into a cheese or the like in alternately twisted condition. When such doubled-yarn is drawn out, untwisting is involved, but since the elastic and non-elastic yarns are drawn out in the same proportions, it follows that there will be no problem in practice in using it in knitting operation on the knitting machine even if it is not set in intimately twined condition as in covered yarn.
In the yarn package obtained by such method, however, it is the undeniable fact that the twist is hard in some places and soft in other places and that at point where the direction of twist changes there are so-called twist-free portions extending over a considerable length. This is because it is wound without means of setting the twist as by heat setting. If the elastic yarn used is very fine, e.g. 20 deniers, the doubled yarn, when left for a day or two on a cheese will temporarily retain the stretched condition, so that the doubled yarn which has been alternately twisted can be maintained in that condition even wound into a cheese. However, if the elastic yarn is 40 deniers or above, such temporary strain is so small in amount that upon being stretched the yarn begins to untwist continuously.
In doubling elastic and non-elastic yarns together, subjecting the doubled yarn to alternate twisting and winding the yarn, the present invention is intended to obtain a doubled yarn package of elastic and non-elastic yarns wherein the alternate twist in the elastic yarn and in the non-elastic yarn is stably retained while minimizing the twist-free portions.